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Bogging under acceleration

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Old Aug 14, 2022 | 06:46 PM
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Bogging under acceleration

Hey everyone, I've been chasing an issue with my firebird for almost two years now. I can idle (it's sporadic) and accelerate (but I have to be slow, if I stomp on it from idle it'll bog and then choppily climb in revs). I also have starting issues, I have to feather the throttle for it to settle at idle. I've replaced the tps (and set it to the correct voltage and verified that it climbs linearly) and put bosch 3's in trying to chase this. It definitely runs better than it did before, but nowhere near "normal". It idles ok and wont die on its own. When i stomp on it theres a sort of "spelunking" noise that comes from the intake and a sudden increase in intake suction that quickly drops as it bogs. After the bogging it'll climb in revs but it's choppy. Does this seem more like a vacuum leak issue or a fuel starvation issue? The only fuel component left to replace is the fuel pump itself... but if it's not the problem I'm not trying to drop the whole rear end of the car lol. Any tips would be appreciated, it seems sort of like what Kincer described in recent posts, but different enough that I'd love some help. Thanks!
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Old Aug 14, 2022 | 06:59 PM
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Komet's Avatar
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Car: 1989 IROC-Z
Engine: L98 350 TPI
Transmission: 700R4
Axle/Gears: BW 9 Bolt / 2.77 Posi
Re: Bogging under acceleration

Check fuel pressure, checking for vacuum leaks would also be a good idea.
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Old Aug 14, 2022 | 07:05 PM
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From: Western Pa
Car: 1989 Trans Am
Engine: 305 H.O. TPI
Transmission: Auto 700R4
Axle/Gears: 3.42 posi
Re: Bogging under acceleration

Originally Posted by 88tpi5spd
Hey everyone, I've been chasing an issue with my firebird for almost two years now. I can idle (it's sporadic) and accelerate (but I have to be slow, if I stomp on it from idle it'll bog and then choppily climb in revs). I also have starting issues, I have to feather the throttle for it to settle at idle. I've replaced the tps (and set it to the correct voltage and verified that it climbs linearly) and put bosch 3's in trying to chase this. It definitely runs better than it did before, but nowhere near "normal". It idles ok and wont die on its own. When i stomp on it theres a sort of "spelunking" noise that comes from the intake and a sudden increase in intake suction that quickly drops as it bogs. After the bogging it'll climb in revs but it's choppy. Does this seem more like a vacuum leak issue or a fuel starvation issue? The only fuel component left to replace is the fuel pump itself... but if it's not the problem I'm not trying to drop the whole rear end of the car lol. Any tips would be appreciated, it seems sort of like what Kincer described in recent posts, but different enough that I'd love some help. Thanks!
Mine ended up being a bad ignition coil, I replaced a lot of stuff to find this out, since you've changed injectors make sure your fuel pressure is good, if it's good I''m betting it's an ignition issue, cap, rotor, icm, or coil. Mine is running fantastic now, FINALLY
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Old Aug 14, 2022 | 07:07 PM
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Re: Bogging under acceleration

Thanks guys, I'll check the fuel pressure tomorrow. Glad to hear it Kincer, hopefully I'll get there soon too!
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Old Dec 30, 2022 | 08:08 PM
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Re: Bogging under acceleration

It's been a minute... finally back from school long enough to work on the car. Fuel gauge hooked up. Key in "ON" position yields 10-15 psi! Should be between 42-47 right?? Seems like a Fuel pump change should be in order right?
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Old Dec 30, 2022 | 08:48 PM
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From: WA
Car: 1989 IROC-Z
Engine: L98 350 TPI
Transmission: 700R4
Axle/Gears: BW 9 Bolt / 2.77 Posi
Re: Bogging under acceleration

More like 38-43 psi, but yeah if it isn't getting close to that then you most likely have a dying fuel pump.
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Old Dec 30, 2022 | 08:53 PM
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Re: Bogging under acceleration

Oh ok. Just gonna go for it and enjoy the experience of taking the whole rear of the car out lol. I'll update once process is done
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Old Jan 6, 2023 | 04:01 PM
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Re: Bogging under acceleration

Welp, that did it. Runs mint now! Dropping the fuel tank wasn't as bad as people made it out to be lol, definitely easier with another person present though.
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Old Jan 8, 2023 | 01:29 PM
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Car: 1988 Pontiac Firebird Formula
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Re: Bogging under acceleration

Originally Posted by 88tpi5spd
Welp, that did it. Runs mint now! Dropping the fuel tank wasn't as bad as people made it out to be lol, definitely easier with another person present though.
A second warm body makes ANY job easier.
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